The present invention relates to a novel process for inhibiting the browning of produce.
Sulfite containing compounds have been used as anti-browning agents, ie; to keep raw or peeled vegetables and fruits from discoloring. Unfortunately, the use of sulfites in conjunction with fresh produce causes certain medical problems with the ultimate consumer of the produce. For example, asthmatics are deemed to be accutely susceptible to sulfites. Certain governmental authorities now require the marking of packaged goods containing more than 10 parts per million of sulphur dioxide equivalent.
In addition, sulfites have been banned by certain governmental authorities for use on fresh vegetables and fruits, including peeled potatoes.
Browning of peeled produce is undesirable, being unaesthetic and perceived to indicate spoiling in the produce. One of the chemical reactions which causes the browning of cut or damaged vegetable surfaces is normally referred to as phenolase (enzymatic) browning. It is believed that damaged or cut vegetable tissue, when exposed to air enhances the enzymatic oxidation of natural phenolase substrates to orthoquinones. Subsequently, the orthoquinones rapidly polymerize to form brown pigments or melanins. Such oxidation is catalyzed by enzymes known as phenolase or polyphenol oxide, tyrosinase, and catecholase. More over, enzymatic browning of this type requires four essential components; oxygen, a particular enzyme, copper, and a substrate. To control browning, one of the essential components must be eliminated. Removing oxygen from the exposed surfaces of vegetables is difficult and expensive to attain in large scale food processing facilities. Phenolase enzymes are naturally present in the fruits and vegetables being treated for browning and are not easily removed therefrom. For example, steam blanching of produce to remove phenolase enzymes causes undesirable softening of the products.
The employment of prior art chelating agents to remove copper from produce has only slowed the browning reaction, not completely eliminating the same. It should be noted that citric acid has been tried as a chelating agent, but such attempts have been unsuccessful in preventing phenolase browning.
It is also important that an treatment to prevent browning in cut fresh raw fruits and vegetables be compatible with governmental findings as to the biological safety of chemical compounds. U.S. Pat. No. 4,097,612 describes the use a three step immersion process in solutions of citrate, and sulfur dioxide, a second solution of alkali metal pyrophosphate, and a third aqueous solution of an alkaline earth metal salt. U.S. Pat. No. 4,221,819 describes an process for treating shrimp which employes an aqueous solution containing a phosphate salt in the presence of traces metals, such as calcium and magnesium, to preserve the texture of the shrimp when it is later cooked and consumed.
A process which inhibits phenolase browning of cut produce in substitution for sulfite containing compounds would be a notable advance in the food processing industry.